The present invention is particularly intended for use on commercial vehicles, although it may be used on any internal combustion engine connected to multiple fuel tanks. In particular, diesel engines typically operate by drawing fuel from a fuel tank, combusting a portion of the fuel and then returning the unused, or uncombusted, fuel to the fuel tank. Depending on engine loading conditions, a substantial volume of fuel drawn from the tank is unused by the engine and returned to the fuel tank. Accordingly, such draw and return assemblies play a vital role in the operation of diesel engines.
Heavy duty commercial vehicles, such as long haul tractor trailers, typically include dual fuel tanks, also called saddle tanks, wherein fuel is drawn simultaneously from both tanks for combustion within the engine. To prevent uneven fuel tank levels, which may lead to air being drawn into the engine, a means of balancing return fuel flow, such as draw and bottom return tube assemblies, typically are installed in each of the dual fuel tanks. One prior art draw and return tube assembly comprises draw and return tubes connected to a flange at one end and connected by a bracket at another end opposite the flange. The flange typically is mounted on an upper inside surface of the fuel tank such that the other, bracketed end of the tubes extends downwardly into the fuel held within the lower portion of the tank. Draw and return lines are connected to the flange, and thereby connected to the draw and return tubes. The draw and return line connectors typically are manufactured in unique predetermined diameters, often times differing from one truck maker to the next, and often times very different from the diameters of available, off-the-shelf drawn tubing. Identical draw and return tube assemblies are typically positioned in each of the two saddle tanks and are each connected to corresponding draw and return lines extending to the truck engine.
The tube openings opposite the flange typically extend away from one another and are each positioned an equal distance from the flange so that the draw and return tube fuel openings are also each positioned an equal distance below the top surface of fuel held within the tank. In this arrangement, when the two tanks and the corresponding draw and return tube assemblies are each positioned at a similar horizontal level on the commercial vehicle, the pressure head of fuel positioned above the draw and return tube openings of each assembly will result in equal amounts of fuel being withdraw from each of the tanks and equal amounts of fuel being returned to each of the tanks. In addition, swedging or crimping of the end of the return tube opening opposite the flange will facilitate complete filling of the return tube. Accordingly, the draw and return tube assemblies of the prior art act as passive flow regulators for ensuring equal levels of fuel drawn and returned to each of the two saddle fuel tanks.
The process for manufacturing these prior art draw and return tube assemblies is quite time consuming and can be very expensive. The prior art process of manufacturing the assembly typically involves purchasing the drawn tubing in a predetermined size. Drawn tubing, such as aluminum drawn tubing, is relatively expensive to manufacture and is cost prohibitively expensive to manufacture in custom sizes. Moreover, small manufacturing operations often times cannot afford to draw their own tubing so that these manufacturers are required to purchase standard sized off-the-shelf drawn tubing. Accordingly, the draw and return tube assemblies of the prior art are manufactured with drawn tubing in one of a few predetermined sizes, regardless of the size tubing desired or required for the particular draw and return tube assembly.
The drawn tube is first cut to a particular length and conveyed under a gas flame or through a heating oven to anneal one end of the tube. This annealing step softens the tube and renders it more ductile thereby facilitating flaring of the tube. The annealed end of the tube is then flared to a size corresponding to the desired inner diameter for threading to a standard pipe thread which will match the corresponding draw or return line connector from the engine. In some cases, a drawn tube having an outer diameter of approximately 0.75 inch (in) (1.88 centimeters (cm)), must be flared as much as 0.2 in (0.5 cm), to an outer diameter of approximately 0.94 in (2.35 cm) in order to fit the corresponding connection to the draw or return line.
Flaring of the drawn tubing takes place in a flaring machine with hydraulic oil used as a lubricant. Prior to welding the flared tube to the flange, the hydraulic oil must be completely cleaned from the tube. This cleaning step produces environmental waste in the form of used hydraulic oil and detergents which must be disposed of in accordance with environmental regulations. Accordingly, this cleaning step can be quite costly.
After cleaning, the tube is then positioned on a bending machine. One end of the tube is then bent to the desired specifications. The other end of the tube, which has been flared, may also be bent and is positioned adjacent the flange and welded thereto. After welding, the inside surface of the flared end that has been welded to the flange is tapped to create threads. A bracket is then placed near the ends of the tubes opposite the flange to stabilize the assembly. The draw and return tube assembly is then ready for installation into a fuel tank and for connection to the connectors of the draw and return fuel lines.
The entire process of cutting, heating, flaring, cleaning, bending, positioning, welding, and then tapping takes approximately 41/2 minutes for each tube, and approximately 9 minutes for each draw and return tube assembly. The steps of heating, flaring and cleaning take approximately one third of the allotted time frame. Accordingly, eliminating the heating, flaring and cleaning steps from the process will reduce the processing time by one third. Eliminating these steps will also reduce the processing costs. Moreover, eliminating the cleaning step will eliminate waste products that currently are placed in hazardous material disposal landfills. There is a need, therefore, for a draw and return tube assembly that can be manufactured without creating hazardous waste products, and which can be manufactured in a variety of connector sizes for use with a variety of draw and return tube lines of different commercial vehicle manufacturers.